The SI unit of frequency, defined as a frequency of 1 cycle per second.

After Heinrich Rudolf Hertz (1857-1894), the German physicist, who made several important
contributions to the study of electromagnetism.

Hertz experiment

آزمایش ِ هرتز

âzmâyeš-e Hertz (#)

Fr.: expérience de Hertz

A laboratory experiment carried out by Heinrich Hertz in 1888 to generate and detect
→ electromagnetic waves for the first time. It involved a
high voltage power source, consisting of two → capacitors,
each provided with a conducting rod. The rods were separated by a small
→ spark gap and connected to an
→ induction coil. When the electrodes were raised to a sufficiently high
→ potential difference, a spark passed across the gap,
and an oscillating discharge took place. A group of waves
with a wavelength of a few meters were emitted at each discharge. A wire loop
provided with a detecting spark gap, held away from the oscillating sparks,
produced sparks upon arrival of the
oscillating electric and magnetic fields.

An electrical system used for the production of
→ electromagnetic waves. It consists of two equal
→ capacitors connected to two
electrodes with a → spark gap between
the electrodes. The system is connected to an → induction coil.
When the induction coil is activated, electromagnetic waves are generated across
the spark gap. See also → Hertz experiment.

Named after the Danish Ejnar Hertzsprung (1873-1967) and the American
Henry Norris Russell (1877-1957). However,
the first H-R diagram was published not by Hertzpurung neither Russell,
but by a PhD student of Karl Schwarzschild at Göttingen. The student was
Hans Rosenberg (1879-1940), who in 1910 published the diagram for stars in the
→ Pleiades
(Astronomische Nachrichten, Vol. 186 (4445), p. 71, 1910).
Although Hertzpurung had a very preliminary diagram in
1908, his first proper diagram was published in 1911. Likewise, Russell published his
version only in 1915 with the better and more numerous data then available
(Nielsen, A.V., 1969, Centaurus 9, 219;
Valls-Gabaud, D., 2002, Observed HR diagrams and stellar evolution,
ASP Conf. Proceedings, Vol. 274. Edited by Thibault Lejeune and João Fernandes);
→ diagram.